The use of metal, such as steel, in forming wear components is ubiquitous. To provide steel components with enhanced surface properties and wear resistance, one very popular technique is to alter the composition of the steel alloy during fabrication to provide an outer surface with high corrosion resistance. Besides being resistant to troublesome corrosion and staining, this “stainless” steel as it is commonly known provides low maintenance and is relatively inexpensive to fabricate, which makes it an ideal base material for a host of commercial applications. In particular, stainless steel can be worked into components, such as sheets, plates, bars, wire, and tubing to be used in cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment (such as for conveying products), and even building material in skyscrapers and large buildings.
While users of stainless steel benefit from the concomitant advantages described above, this material is not without limitations, especially when used in industrial applications involving the processing of organic materials. For one, stainless steel can have a relatively high coefficient of friction with many other materials, including plastics (such as acetal) and other metals. Thus, stainless steel is generally not used in environments where it is subjected to constant or frequent sliding contact with another part, since the resulting high friction creates undesirable wear and may quickly degrade the desirable corrosion-resistant surface.
Wearing of stainless steel over time also tends to produce what is known in the vernacular as “black oxide.” This black oxide is believed to emanate from the surface of the stainless steel as the result of abrasion. Although generally believed to be harmless, this black oxide is unsightly, difficult to remove using standard cleaning techniques, and leads users of the components to believe that the affected components must be replaced to ameliorate the problem. While offering a temporary improvement, replacing the components before the end of their normal service life is an expensive undertaking and merely delays the onset of a relapse of the problem.
For reasons not well identified, the typical surface properties of common types of stainless steel also cause certain materials, and especially those with a relatively high fat (oil) content, to tend to adhere and resist being released during cleaning. For example, stainless steel is often used for conveying, such as through chutes, dispensers, chains, belts, or like components. Typically, these conveyor components must be washed frequently and thoroughly in order to ensure that a clean environment is maintained and contamination kept in close check, especially when products for human consumption are involved (primarily, because of strict FDA regulations).
Despite offering superior corrosion resistance, the property of stainless steel that allows certain materials to adhere to it makes it more difficult and expensive to wash thoroughly. Indeed, washing may take up to one third of the service life of the component, which obviously contributes significantly to the operational cost. Besides being costly, frequent washing also generates a significant amount of waste product requiring further treatment or disposal, which raises environmental considerations. Washing is also typically done using chlorine, which as is well known can easily degrade stainless steel over time, and even lead to deleterious rusting.
Accordingly, a need is identified for an improved manner of making metals and, in particular, stainless steel, into components usable in situations where they are subject to sliding friction and concomitant wear, or where cleanability is of paramount importance, such as in food and chemical processing. No significant increase in manufacturing expense would result, yet a significant benefit in terms of service life and cleanability would be realized. Furthermore, the technique would be such that it could be used not only in manufacturing new components, but also on existing components in order to extend their service life and improve cleanability.